This page details the steps taken to determine the most appropriate time period definitions for the Triangle Regional Model (TRMG2). Once determined, this page also determines the directionality, occupancy, and capacity factors for each time period. Caliper used the processed household survey to perform the analysis.
(To skip to the final period definitions, click here.)
Peak period determination is based on an analysis of the trips in motion throughout the day. First, the day is broken up into 15-minute increments. A trip from the household survey is said to be “in motion” if any portion of the trip occurs within the 15-minute bin. As a result, a single trip can be counted in multiple bins. Determining the peak period considers the distribution of all trips as well as the distribution of trips on work tours individually. The chart below shows these two distributions, which look as expected with the AM peak being shorter and more condensed than the PM.
The next step is to determine the peak hour for all trips and those on work tours. In the tables below, the AM and PM peak hours by type are presented. At a minimum, the AM and PM peak periods should contain the respective peak hour for work trips and all trips. The chart below shows that the peak hour for work and all trips are exactly the same in the Triangle region based on the surveys as is often, but not always, the case.
| Trip Purpose | Peak Start | Peak End |
|---|---|---|
| Work | 07:15:00 | 08:15:00 |
| All | 07:15:00 | 08:15:00 |
| Trip Purpose | Peak Start | Peak End |
|---|---|---|
| Work | 16:00:00 | 17:00:00 |
| All | 16:15:00 | 17:15:00 |
Based on the trips in motion profile, there are four distinct periods of the day. AM and PM peaks have the highest intensity of trip making, followed by mid-day, with the overnight period containing the fewest trips in motion. Boundaries for these periods are defined such that the variance of trips in motion within periods is smallest while variance between periods is largest.
The final period definitions are shown in the table below including the mid-day (MD) period. The remaining hours of the day are captured in the night (NT) period. In the chart, the final period is represented by the gray rectangle.| Period | From | To | Hours |
|---|---|---|---|
| AM | 07:00:00 | 09:00:00 | 2 |
| MD | 09:00:00 | 15:00:00 | 6 |
| PM | 15:00:00 | 18:00:00 | 3 |
| NT | 18:00:00 | 07:00:00 | 13 |
The table below shows the average 15-minute trips in motion during each period. These period definitions accurately capture the disparate characteristics of each.
| Time of Day | Mean Trips in Motion |
|---|---|
| AM | 49355 |
| MD | 36053 |
| PM | 50047 |
| NT | 9889 |